INTRODUCTION autoexpect watches you interacting with
another program and creates an Expect script that reproduces
your interactions. For straightline scripts, autoexpect
saves substantial time over writing scripts by hand. Even if
you are an Expect expert, you will find it convenient to use
autoexpect to automate the more mindless parts of
interactions. It is much easier to cut/paste hunks of
autoexpect scripts together than to write them from scratch.
And if you are a beginner, you may be able to get away with
learning nothing more about Expect than how to call
autoexpect.

The simplest way to use autoexpect is to call it from
the command line with no arguments. For example:

% autoexpect

By default, autoexpect spawns a shell for you. Given a
program name and arguments, autoexpect spawns that program.
For example:

% autoexpect ftp ftp.cme.nist.gov

Once your spawned program is running, interact normally.
When you have exited the shell (or program that you
specified), autoexpect will cre- ate a new script for you.
By default, autoexpect writes the new script to
"script.exp". You can override this with the -f
flag followed by a new script name.

The following example runs "ftp
ftp.cme.nist.gov" and stores the resulting Expect
script in the file "nist".

% autoexpect -f nist ftp ftp.cme.nist.gov

It is important to understand that autoexpect does not
guarantee a working script because it necessarily has to
guess about certain things - and occasionally it guesses
wrong. However, it is usually very easy to identify and fix
these problems. The typical problems are:

· Timing. A surprisingly large number of programs
(rn, ksh, zsh, telnet, etc.) and devices (e.g., modems)
ignore keystrokes that arrive "too quickly" after
prompts. If you find your new script hanging up at one spot,
try adding a short sleep just before the previous send.

You can force this behavior throughout by overriding the
variable "force_conservative" near the beginning
of the gen- erated script. This "conservative"
mode makes autoexpect automatically pause briefly (one tenth
of a second) before sending each character. This pacifies
every program I know of.

This conservative mode is useful if you just want to
quickly reassure yourself that the problem is a timing one
(or if you really dont care about how fast the script runs).
This same mode can be forced before script generation by
using the -c flag.

Fortunately, these timing spots are rare. For example,
tel- net ignores characters only after entering its escape
sequence. Modems only ignore characters immediately after
connecting to them for the first time. A few programs
exhibit this behavior all the time but typically have a
switch to disable it. For example, rns -T flag disables this
behavior.

The following example starts autoexpect in conservative
mode.

autoexpect -c

The -C flag defines a key to toggle conservative mode.
The following example starts autoexpect (in non-conservative
mode) with ^L as the toggle. (Note that the ^L is entered
literally - i.e., enter a real control-L).

autoexpect -C ^L

The following example starts autoexpect in conservative
mode with ^L as the toggle.

autoexpect -c -C ^L

· Echoing. Many program echo characters. For
example, if you type "more" to a shell, what
autoexpect actually sees is:

Without specific knowledge of the program, it is
impossible to know if you are waiting to see each character
echoed before typing the next. If autoexpect sees characters
being echoed, it assumes that it can send them all as a
group rather than interleaving them the way they originally
appeared. This makes the script more pleasant to read.
However, it could conceivably be incorrect if you really had
to wait to see each character echoed.

· Change. Autoexpect records every character from
the inter- action in the script. This is desirable because
it gives you the ability to make judgements about what is
important and what can be replaced with a pattern match.

On the other hand, if you use commands whose output
differs from run to run, the generated scripts are not going
to be correct. For example, the "date" command
always produces different output. So using the date command
while running autoexpect is a sure way to produce a script
that will require editing in order for it to work.

The -p flag puts autoexpect into "prompt
mode". In this mode, autoexpect will only look for the
the last line of program output - which is usually the
prompt. This handles the date problem (see above) and most
others.

The following example starts autoexpect in prompt mode
with ^P as the toggle.

autoexpect -p -P ^P

OTHER FLAGS The -quiet flag disables informational
messages produced by autoexpect.

The -Q flag names a quote character which can be used to
enter charac- ters that autoexpect would otherwise consume
because they are used as toggles.

The following example shows a number of flags with quote
used to pro- vide a way of entering the toggles
literally.

autoexpect -P ^P -C ^L -Q ^Q

STYLE I dont know if there is a "style" for
Expect programs but autoexpect should definitely not be held
up as any model of style. For example, autoexpect uses
features of Expect that are intended specifically for
computer-generated scripting. So dont try to faithfully
write scripts that appear as if they were generated by
autoexpect. This is not use- ful.

On the other hand, autoexpect scripts do show some
worthwhile things. For example, you can see how any string
must be quoted in order to use it in a Tcl script simply by
running the strings through autoexpect.

SEE ALSO "Exploring Expect: A Tcl-Based Toolkit for
Automating Interactive Pro- grams" by Don Libes,
OReilly and Associates, January 1995.

AUTHOR Don Libes, National Institute of Standards and
Technology

expect and autoexpect are in the public domain. NIST and
I would appreciate credit if these programs or parts of them
are used.